What type of indication is used for reverse flow control in positive shutoff valves?

Reverse flow control in positive shutoff valves is crucial for ensuring the safety and proper operation of LPG systems. The use of reverse flow indicators specifically serves to detect and prevent any unintended reverse flow of gas. These indicators monitor the direction of the gas flow, which is vital in applications where backflow could lead to dangerous situations such as contamination or pressure fluctuations.

In contexts where LPG is used, maintaining a controlled flow direction is essential. If the flow were to reverse, it could pose risks not only to equipment but also to safety. Hence, having a dedicated mechanism, like reverse flow indicators, allows operators to quickly identify any changes in flow direction, ensuring immediate corrective action can be taken. This form of indication supports the overall integrity of the system by actively monitoring and managing flow dynamics.

The other options, while related to monitoring various physical conditions, do not specifically address the unique requirement of detecting reverse flow in a valve system.